If the philosophy of immaterialism is true, then the screen you're reading this on is not really there. Neither is chocolate, which seems like a huge loss — but if you can still enjoy its taste, scent, and smoothness, what's the difference?
A philosopher named George Berkeley came up with the idea of immaterialism in the early 1700s. He was concerned that previous philosophers assumed the existence of physical objects outside of our minds, but nobody could actually prove it. All we have to go on, he said, is our perception of things, so why not say that these so-called physical objects are just our perceptions? What is chocolate, apart from someone's mind perceiving a certain taste, color, weight, and texture? Nothing, according to Berkeley.